Rising oil and chemicals manufacturing, especially at the Methanex plant in Taranaki, helped boost total manufacturing sales volumes for the third quarter in a row.

But Statistics NZ figures out today show meat and dairy manufacturing was "relatively flat" in the quarter, after a big gain at the end of last year.

After adjusting for seasonal effects, the volume of total manufacturing sales rose a weaker than expected 0.5 per cent in the March 2014 quarter, led by rises in chemical and petroleum related industries.

The latest gain was modest compared with the big 5.4 per cent lift in the December quarter. The December quarter's jump reflected a post-drought catch-up in dairy exports, Westpac economists said.

After adjusting for inventory changes, Westpac estimated that total manufacturing production rose more than 1 per cent for the third quarter in a row.

But most of that came from the big leap in the petroleum and chemicals sectors.

Overall, Westpac said the manufacturing figures did not change its suspicion that it would need to revise up its March quarter GDP growth forecast from 1.1 per cent.

That was because construction figures out last week were "massively stronger" than expected, offsetting weaker than expected manufacturing and wholesale trade figures, Westpac said.

After adjusting for seasonal effects, the volume of total manufacturing sales rose 0.5 per cent in the March 2014 quarter, led by rises in chemical and petroleum-related industries.

The latest gain was modest compared with the big 5.4 per cent lift in the December quarter.

Chemical, polymer, and rubber product manufacturing was up 8.5 per cent in the March quarter. That reflected increased capacity and production at the Methanex plants in Taranaki, which has helped lift industry sales of methanol in recent quarters.

Oil and coal product manufacturing was up 5.8 per cent. Oil and coal manufacturing volumes bounce a round heavily and do not follow a stable seasonal pattern.